1. Field of the Invention
The present invention relates to movable body drive methods, movable body drive systems, pattern forming methods, pattern forming units, exposure methods, exposure apparatus, and device manufacturing methods, and more particularly to a movable body drive method in which a movable body is driven in at least a uniaxial direction, a movable body drive system suitable for applying the method, a pattern formation method that uses the movable body drive method, a pattern forming apparatus that is equipped with the movable body drive system, an exposure method that uses the movable body drive method, an exposure apparatus that has the movable body drive system, and a device manufacturing method that uses the pattern forming method.
2. Description of the Background Art
Conventionally, in a lithography process for manufacturing microdevices (electronic devices and the like) such as a liquid crystal display element or the like, a reduction projection exposure apparatus by a step-and-repeat method (the so-called stepper), a scanning projection exposure apparatus by a step-and-scan method (the so-called scanning stepper (also called a scanner)) and the like have been relatively frequently used.
With these types of exposure apparatus, in order to transfer a pattern of a reticle (or a mask) onto a plurality of shot areas on a wafer, the wafer stage that holds the wafer is driven in a XY two-dimensional direction by a linear motor or the like. Especially in the case of a scanning stepper, not only the wafer stage but also the reticle stage is driven in the scanning direction with predetermined strokes by a linear motor or the like. Position measurement of the reticle stage and the wafer stage is normally performed using a laser interferometer, which has good stability of measurement values over a long period of time, and also has high resolution.
However, due to finer patterns that come with higher integration of semiconductor devices, position control of the stages with higher precision is becoming required, and short-term fluctuation of measurement values due to temperature fluctuation of the atmosphere on the beam optical path of the laser interferometer is now becoming a matter that cannot be ignored.
Meanwhile, recently, as a type of a position measurement unit, an encoder that has a measurement resolution of the same level or higher than a laser interferometer has been introduced (refer to, for example, U.S. Pat. No. 6,639,686). However, since the encoder uses a scale (grating), various error factors (drift of grating pitch, fixed position drift, thermal expansion and the like) that occur in the scale due to the passage of use time exist, which makes the encoder lack in mechanical long-term stability. Therefore, the encoder has a drawback of lacking measurement value linearity and being inferior in long-term stability when compared with the laser interferometer.